Solar Water Heating as an Energy Service – Part 1 – Technology Choices and Markets

Solar water heaters as a product have the potential to contribute considerably to energy demand reduction in developing countries. This exists both as a household-scale technology, and in industrial applications such as desalination in countries such as the UAE and Saudi Arabia, and industrial process heat in both developed and developing countries. A number of developing countries around the world, notably those in Sub-Saharan Africa, have had success in disseminating solar water heating products on a commercial basis, in addition to a number of large-scale government dissemination programs. Countries such as South Africa (with around 500,000 systems installed as of 2016) and China (which has over 85 million installed SWH units as of 2016) have developed a robust network of commercial installers and manufacturers of solar water heating units and parts, selling products on a market basis to households and businesses.

Solar water heater installed by ESKOM, South Africa. Image: gmourits, Flickr, via http://inhabitat.com/eskom-installs-solar-powered-heaters-on-south-african-roofs/

 

There are a number of opportunities in developing country markets to develop a solar water heating sector. A number of developing countries, particularly those in Sub-Saharan Africa, have high levels of insolation (sunlight kWh/m2/day), and a consistent demand across income segments of the population for water heating. Industrial process heat is another sector where solar water heating could have an impact, as is institutional process heat, for example heat exchangers for hospital refrigeration, and hot water for use in health centres and schools.

Entrepreneurs and companies looking to enter the solar water heating market space need to consider a number of questions before starting their operations. Firstly, an appropriate technology choice is essential for succeeding in the SWH market, perhaps more so than many other renewable energy technologies. Deciding which consumer segment or income bracket to target informs the technology decision somewhat, but thorough research needs to be done on what the market and consumers can afford before deciding on a technology. Main technology streams for SWH include flat-plate solar collectors, and evacuated tube solar collectors. Both work on similar principles, heating water that passes through the collector, either through capillary action or through the use of an electric pump. Flat-plate collectors can be slightly less efficient than evacuated tube designs due to heat loss through convection, however they are also less expensive and simpler to produce. Evacuated tube designs are generally more efficient at heating water, but are also more expensive to compensate for the increased complexity in manufacture.

Flat-plate solar collector installed on a house in the United Kingdom. Image: uk.solarcontact.com

Flat-plate solar collector efficiency vs evacuated tube efficiency at various temperature ranges for a typical North American location. Source: https://blog.heatspring.com/solar-thermal-flat-plate-or-evacuated-tube-collectors/

 

When designing a new solar water heating business or intervention, therefore, it is important to consider which variant on the technology is to be used, and at what scale (household, institutional, industrial etc.), in order to plan dissemination based on affordability for the consumer. The next blog in this series will investigate business and financing models that can assist in improving the sustainability and replicability of solar water heating energy service companies.

– Daniel Kerr, UCL Energy Institute

References

Clean Technica (2015) World’s Largest Solar Powered, Jellyfish-Fightin’ Desalination Plant To Be Built in Saudi Arabia. Available at: https://cleantechnica.com/2015/01/22/worlds-largest-solar-powered-desalination-plant-under-way/

Urban, Geall & Wang (2016) Solar PV and solar water heaters in China: Different pathways to low carbon energy. Renewable and Sustainable Energy Reviews, Vol. 64, pp. 531 – 542

EE Publishers (2016) Solar water heater rollout programme gains momentum. Available at: http://www.ee.co.za/article/solar-water-heater-rollout-programme-gains-momentum.html

Side-Stepping the Energy Ladder

For decades now there has been talk of a hierarchy of energy use or ‘ladder’ which defined levels of development as well personal aspirations. Occupying the bottom of this ladder were primary fuels such as biomass, dung, etc. Moving towards the middle we had kerosene and LPG which were considered ‘modern fuels’ because of their comparative convenience as well as fairly sophisticated refining process associated with hydro-carbon fuels. And of course, at the top of the ladder was electricity, the most versatile and modern energy source of them all.

There have been many articles published about the energy ladder, some supportive of its clear albeit simplistic representation of how households progress in terms of fuel use while others have been more critical altogether of its rigidity and inability to accommodate variables such as culture,  differing socio-economic and geographic contexts. How this is playing out in South Africa today is quite interesting. Looking at South Africa’s energy policy, it is highly orientated towards developing the ‘top of the ladder’ options. Policy and regulations abound when it comes to nuclear, coal, large scale renewable, LPG gas, etc. But there is little regulatory interest when it comes to wood. Perhaps its posturing (Africa’s largest and most sophisticated economy requires nuclear not biomass regulations) or perhaps that’s the reality (the energy service activities are at the top of the ladder).

Despite this there are a number of inconsistencies emerging;

• Electricity is becoming increasingly expensive (above inflation increases for over 5 years already with about the same to come) so many poorer households are having to ‘back-switch’ to LPG and paraffin.
• Many middle class households that have been electrified for decades are opting to cook on LPG gas (on stainless steel hobs for sure) and heat their houses in winter using wood (up-market fireplaces).
• Millions of households still cook with wood although they have access to electricity. The energy source is simply uneconomic to support the full range of thermal services households require.
• High oil prices (think kerosene and LPG) and increasing electricity prices are putting strain on the ability of people to use fuels which they have access to. Access and utilisation have become two different issues
• Political promises which have for decades reinforced the energy ladder now cannot be met as lower-income households cannot afford to utilise these fuels for all services required.
• Department of Rural Development and Land Affairs has put out a tender for improved cookstoves, a technology that has never appealed to the Department of Energy because of the ‘poverty’ stigma associated with wood. Or, “people did not struggle [against Apartheid] to use wood” the former Minister of Energy [Dipuo Peters] once said to this blogger [African Minister’s Meeting, Sandton Convention Centre, Johannesburg, 17th September 2011].

Without significant subsidies, the lower-income households will find ascending the so called energy ladder increasingly difficult to achieve. The progressive notion of the ladder had much to do with the assumption that it was simply a matter of time before households, given broader economic growth, would progress up the ladder. However such economic growth hasn’t quite materialised and the associated costs of using these fuels has become increasingly exorbitant. Perhaps the middle-class should be used to assist in de-stigmatising the use of biomass fuels and the like which will at least assist in addressing some of the indignity associated with being trapped at the ‘bottom of the ladder’. Third generation improved cookstoves instead of open fires should go a long way in terms of doing just that.

– Robert Aitken, Restio Energy